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Friction stir spot welding (FSSW) is applied to join advanced high strength steels (AHSS): galvannealed dual phase 780 MPa steel (DP780GA), transformation induced plasticity 780 MPa steel (TRIP780), and hot-stamped boron steel (HSBS). A low-cost Si₃N₄ ceramic tool was developed and used for making welds in this study instead of polycrystalline cubic boron nitride (PCBN) material used in earlier studies. FSSW has the advantages of solid-state, low-temperature process, and the ability of joining dissimilar grade of steels and thicknesses. Two different tool shoulder geometries, concave with smooth surface and convex with spiral pattern, were used in the study. Welds were made by a 2-step displacement control process with weld time of 4, 6, and 10 seconds. Static tensile lap-shear strength achieved 16.4 kN for DP780GA-HSBS and 13.2 kN for TRIP780-HSBS, above the spot weld strength requirements by AWS. Nugget pull-out was the failure mode of the joint.

Currently the U. S. Department of Defense (DoD) exclusively uses potassium acetate (KAc)-based runway deicing fluids (RDFs) to deice and anti-ice military runways and taxiways. Commercial airports predominantly use KAc, but some also use RDFs composed of KAc plus propylene glycol (PG) or urea plus PG. Conventional RDFs have environmental concerns due to toxicity as well as material compatibility problems such as corrosion of aircraft carbon brake-pad components, cadmium-plated landing gear, and airfield lighting fixtures. Under the Strategic Environmental Research and Development Program (SERDP), Battelle tested a series of patented - bio-based RDFs to address these issues. Tests showed that the Battelle RDFs met the mandatory Aerospace Material Specification (AMS) 1435 requirements. These new RDFs have reduced ecotoxicity compared to currently used RDFs and are compliant with all other environmental requirements.

In the new design, the electrode employs composite electrode face construction with dissimilar materials. A cylindrical insert located in the electrode face center is made of low thermal and electrical conductivity material, such as stainless steel, and an annular outer sleeve is made of stainless steel and located at periphery of the electrode. Base material of the electrode is still made of copper alloys. With this electrode design, the electrical-thermal-mechanical conditions can be improved by confining the current flow path to reduce current level required for the weld nugget formation, and optimizing electrode pressure distribution, and minimizing electrode face heating and plastic deformation.

This paper addresses the modeling issues of resistance spot welds. The state of the art modeling techniques on weld process simulation, weld property prediction and weld engineering performance evaluation are presented. First, weld process simulation is performed using the incrementally coupled thermal-electrical-mechanical analyses. The resulted weld nugget size, weld residual stress and weld material property distributions are then used in determining the static performance of a single weld coupon. Comparisons with experimental measurements are presented as validations. Results generated from this single weld coupon is then used in the simulation of dynamic crush mechanism of a spot welded single hat section.

An important emerging technical area is computer-based modeling of the various manufacturing processes that are used in many diverse industries. These models are used to optimize manufacturing techniques to reduce fabrication costs and improve the service performance. One manufacturing process important in steel fabrication is welding. It can be a useful tool to aid in reducing fabrication costs and service durability by optimizing the weld process and is the subject of this paper.

This paper presents a numerical analysis of the effect of weld induced residual stress on the fatigue behavior of a T-joint. The thick-section T-joint contained 18 individual weld passes and was subjected to fully-reversed, zero-maximum, and zero-minimum fatigue cycling. The effect of the residual stress was demonstrated by comparing the result with and without residual stress. It was concluded that the local fatigue parameters (mean stress, alternating stress, and stress ratio) at the suspected crack initiation site were changed significantly by the residual stresses when the applied stress were other than fully reversed. In addition, the effect of the stress concentration at the weld was more significant that the effect of the residual stress for the applied fatigue loads levels that were considered. The analysis method presented can be used to assess weldment design and process variables.

The cost of electroplating zinc die castings can be reduced by employing microcracked or microporous chromium in place of conventional chromium; the former is more effective in improving corrosion performance while conserving nickel. Exposure data are examined and specifications for nickel and chromium content are presented.